FixVacuum does not replace tile air if there are no adjacent tiles. (#9535)

Content.Server/Atmos/EntitySystems/AtmosphereSystem.GridAtmosphere.cs

@@ -440,6 +440,10 @@ public sealed partial class AtmosphereSystem
 
         var adjacent = adjEv.Result!.ToArray();
 
+        // Return early, let's not cause any funny NaNs or needless vacuums.
+        if (adjacent.Length == 0)
+            return;
+
         tile.Air = new GasMixture
         {
             Volume = GetVolumeForTiles(mapGridComp.Grid, 1),
@@ -449,10 +453,6 @@ public sealed partial class AtmosphereSystem
         tile.MolesArchived = new float[Atmospherics.AdjustedNumberOfGases];
         tile.ArchivedCycle = 0;
 
-        // Return early, let's not cause any funny NaNs.
-        if (adjacent.Length == 0)
-            return;
-
         var ratio = 1f / adjacent.Length;
         var totalTemperature = 0f;